What are the treatment options for Irritable Bowel Syndrome (IBS) constipation?

Treatment of IBS with Constipation (IBS-C)

Start with soluble fiber (ispaghula/psyllium) at 3-4 g/day, gradually increasing to avoid bloating, combined with regular physical exercise as foundational therapy; if symptoms persist after 4-6 weeks, add polyethylene glycol (PEG) as an osmotic laxative, and if still inadequate after 3 months, escalate to linaclotide 290 mcg daily on an empty stomach as the preferred prescription agent. 1

First-Line Treatment: Lifestyle and Dietary Modifications

Begin with these foundational interventions before any pharmacological therapy:

• Regular physical exercise should be recommended to all IBS-C patients as this improves global symptoms and forms the foundation of treatment 1, 2
• Soluble fiber supplementation with ispaghula or psyllium starting at 3-4 g/day, building up gradually to avoid bloating and gas, is effective for both global symptoms and abdominal pain 1, 2, 3
• Avoid insoluble fiber (wheat bran) as it consistently worsens IBS-C symptoms, particularly bloating 1, 2, 3
• Adequate time for regular defecation should be advised, particularly establishing a routine 2

If soluble fiber fails after 4-6 weeks, consider a supervised low FODMAP diet as second-line dietary therapy, delivered in three phases (restriction, reintroduction, personalization) by a trained dietitian with planned reintroduction of foods according to tolerance 1, 3

Critical Dietary Pitfalls to Avoid

• Do not recommend IgG antibody-based food elimination diets as they lack evidence and may lead to unnecessary dietary restrictions 1, 2
• Do not recommend gluten-free diets unless celiac disease has been confirmed 1, 2

Second-Line Treatment: Osmotic Laxatives

When first-line measures are inadequate:

• Start polyethylene glycol (PEG) as an osmotic laxative, titrating the dose according to symptoms; abdominal pain is the most common side effect 1, 2
• Continue soluble fiber alongside PEG as it has demonstrated efficacy for global IBS symptoms and can work synergistically 1
• Review efficacy after 3 months and discontinue if no response 1

Third-Line Treatment: Prescription Secretagogues

For patients who fail first-line therapies after 3 months:

• Linaclotide 290 mcg once daily on an empty stomach is the preferred second-line prescription agent with high-quality evidence supporting its use for both abdominal pain and constipation 1, 2, 4
• Must be taken at least 30 minutes before the first meal of the day to maximize efficacy 1
• Diarrhea is the most common adverse event with linaclotide, occurring as the mechanism of action 1
• Review efficacy after 3 months and discontinue if no response 1

Alternative secretagogues if linaclotide is not tolerated or not covered by insurance:

• Lubiprostone 8 mcg twice daily with food is FDA-approved for women with IBS-C, though it has a conditional recommendation with moderate certainty evidence 1, 5
• Nausea is the most common side effect of lubiprostone (19% vs 14% with placebo); taking with food reduces nausea 1, 5
• Plecanatide is another alternative secretagogue with similar efficacy to linaclotide 1

Fourth-Line Treatment: Stimulant Laxatives for Refractory Cases

If secretagogues fail or are not tolerated:

• Bisacodyl 10-15 mg once daily, with a goal of one non-forced bowel movement every 1-2 days 1
• Can increase to 10-15 mg twice or three times daily if constipation persists after 2-4 weeks 1
• Sodium picosulfate (a stimulant laxative) can be used instead of bisacodyl 1

Treatment for Refractory Abdominal Pain: Neuromodulators

For persistent abdominal pain despite adequate treatment of constipation:

• Tricyclic antidepressants (TCAs) are the most effective option for refractory abdominal pain and global symptoms 1, 2, 3
• Start amitriptyline 10 mg once daily at bedtime, titrated slowly (by 10 mg/week) to 30-50 mg daily 1, 2
• Critical warning: TCAs may worsen constipation through anticholinergic effects, so ensure adequate laxative therapy is in place before starting 1
• Continue for at least 6 months if the patient reports symptomatic improvement 1, 2
• Explain the rationale clearly to patients, as these are used for pain modulation via gut-brain interaction, not for depression 2, 3

Alternative neuromodulator:

• SSRIs may be effective as second-line neuromodulators for global symptoms when TCAs are not tolerated or worsen constipation 1, 2, 3

Psychological Therapies for Persistent Symptoms

When symptoms persist despite 12 months of pharmacological treatment:

• IBS-specific cognitive behavioral therapy (CBT) is effective for global symptoms with strong recommendation 1, 2, 3
• Gut-directed hypnotherapy is effective for global symptoms with strong recommendation 1, 2, 3
• These brain-gut behavior therapies are specifically designed for IBS and differ from psychological therapies that target depression and anxiety alone 3

Critical Pitfalls to Avoid in IBS-C

What NOT to prescribe:

• Do not prescribe anticholinergic antispasmodics like dicyclomine or hyoscyamine in IBS-C, as they reduce intestinal motility and enhance water reabsorption, which will worsen the constipation 1
• Do not continue docusate (Colace) as evidence demonstrates it lacks efficacy for constipation 1
• Do not use opioids for chronic abdominal pain management due to risks of dependence and complications 1, 2

Treatment Monitoring Algorithm

Follow this timeline for treatment adjustments:

1. After 4-6 weeks of soluble fiber: If inadequate response, add PEG 1
2. After 3 months of PEG: If inadequate response, escalate to linaclotide 1
3. After 3 months of linaclotide: If inadequate response, consider bisacodyl or refer for psychological therapies 1
4. Throughout treatment: If abdominal pain is refractory despite adequate treatment of constipation, add amitriptyline 1, 2

Managing patient expectations is crucial, as complete symptom resolution is often not achievable; the goal is symptom relief and improved quality of life 1, 2